Methanation is a process of creating synthetic natural gas (methane) by combining carbon dioxide or carbon monoxide and hydrogen. 

The chemical processes used are shown below:

One carbon monoxide molecule combines with three hydrogen molecules to create one methane molecule and one water molecule:

CO + 3 H2 à CH4 + H2O


One carbon dioxide molecule combines with four hydrogen molecules to create one methane molecule and two water molecules: 

CO2 + 4 H2 à CH4 + 2 H2O


The reactions are exothermic, meaning that they give off energy in the form of heat. 

Methanation is currently used in ammonia plants and in a few coal to syngas applications. In the future it may be used as a means of creating renewable synthethic natural gas by combining green hydrogen (created using renewable electricity) with carbon dioxide captured from industrial or electric generation processes. One technology which could assist with decarbonization efforts is biomethanation. This uses microorganisms in a bioreactor to combine carbon dioxide and water. 


Source: SoCalGas